Chromosome suppression of tumorigenicity, cell proteins related to tumorigenicity, gene transfer, and gene regulation and interaction in mammalian cells are the main areas of investigation. Our current findings that in cell hybrids specific combinations of normal human chromosomes suppress the ability of some heteroploid human and mouse cells to form tumors in nude mice are to be extended to determine if these same chromosomes will suppress tumorigenic cells of varied origins. Attempts will then be made to map the chromosomal location of such suppressor information by using cells from individuals with structural rearrangements or deletions of these chromosomes. Simultaneously two dimensional electrophoretic techniques will be used to attempt to identify in these same hybrids and other appropriate cell systems new or altered cell surface membrane proteins specifically associated with tumorigenicity with the long-range objective of finding proteins against which tumor specific antisera can be made. Systems which we have developed for transferring what appear to be restricted amounts of genetic information between cells will be extended to determine if such "transgenomes" are stably incorporated into the recipient chromosomes and if so whether this occurs at preferential sites. Hybrids of liver cells of mice, carrying a mutation for the inducible enzyme tyrosine amino transferase (TAT), fused with those of rat liver cells which produce this enzyme, will be used to map the structural and regulatory TAT genes to provide cell systems for exploring gene interaction and regulation. The information gained from the latter two studies may ultimately be applicable to ameliorating some human genetic defects.